Dyestuff applicators of this description have been disclosed in various copending applications of mine including, for example, applications Ser. Nos. 426,909 filed Dec. 20, 1973 (now U.S. Pat. No. 3,949,666) 437,039 filed Jan. 28, 1974, 438,261 filed Jan. 31, 1974 (now U.S. Pat. No. 3,949,667) and 438,282 filed Jan. 31, 1974. The devices disclosed in these prior applications basically comprise a rigid housing, supported on a horizontal supply tube, in which a generally prismatic distributing member is vertically slidable so as to yield to irregularities in the thickness of the substrate. In order to minimize leakage of liquid dyestuff between the distributing member and its guide structure, the discharge slot at the underside of the distributing member may be spanned by membranes or foils with different degrees of resiliency, partly slotted and partly perforated, as described for example in my prior application Ser. Nos. 364,560 filed May 29, 1973 (now U.S. Pat. No. 3,921,520), 376,714 filed July 5, 1973 (abandoned and replaced by Ser. No. 582,925 filed June 2, 1975 ) and 430,389 filed Jan. 3, 1974 (now U.S. Pat. No. 3,942,439).